Adjustable focusing coil



1953 c. E. WALTON 2,648,036

ADJUSTABLE FOCUSING OIL Filed March 12, 1946 2 Sheets-Sheet 1 FIG.2

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INVENTOR. CECIL E. WALTON ATTORNEY Aug. 4, 1953 c. E. WALTON 2,548,036

ADJUSTABLE FOCUSING OIL Filed March 12, 1946 2 Sheets-Sheet 2 FIG.3V J

INVENTOR. CECIL E. WALTON ATTORNEY Patented Aug. 4, 1953 ADJUSTABLE FOCUSING COIL Cecil E. Walton, Cleveland, Ohio, assignor, by mesne assignments, to the Umted States of America as represented by the Secretary of the Navy Application March 12, 1946, Serial N 0. 653,909

This invention relates to focusing coils for cathode ray tubes or similar devices and more particularly to such coils which are adjustable in position to permit more accurate and better focusing of the electron beam of the cathode ray tube.

In a cathode ray tube, electrons are emitted at the cathode, situated at one end of the tube,

' and are accelerated by positive potentials in such a manner as to be directed toward the face of the tube at the opposite end. The inner surface of the face, at this opposite end, has been treated with chemical materials to provide a screen which will emit a fluorescent glow when struck by the accelerated electrons. When the electrons are emitted from the cathode, their initial lines of motion are in diverse directions. The fluorescent spots of light which would appear on the face of the tube when these electrons struck it would be widely scattered, or at best, the glow would spread over too large an area for intelligible use if the electrons were allowed to continue in their initial diverse directions. It is therefore necessary to focus the electron stream so that the points of impact with the face of the tube will result in a sharp and well defined spot of light.

The first step in focusing the electron stream, of course, is accomplished by the action of the control grid which causes the electrons to converge first at a point called the crossover point. But this initial point of focus is at a considerable distance from the face of the tube, conse-' quently additional focusing must be introduced to control the stream of electrons as it progresses from the crossover point to the face.

In a magnetic type cathode ray tube, this additional focusing is accomplished by a magnetic field through which the electrons must pass. 'Io procure this magnetic field, a coil of wire, mounted in a toroidal case made of soft iron or equivalent magnetic material, is placed externally around the neck of the tube in such manner that the magnetic field produced by the coil acts upon .the electron stream. The coil has the additional function of determining the position of the spot on the face of the tube static state of operation. Therefore, in order that the focusing and positioning of the spot upon the face of the tube may be it is necessary that means ithe coil can be adjusted to any position in a plane when the tube is in a.

accurately controlled, be provided whereby perpendicular to the electron stream. Also, since the electron stream is not necessarily parallel with the outer mechanical structure of the tube, additional means must necessarily be pro- 13 Claims. (Cl. 317-200) vided for angular adjustment of the coil plane with respect to the neck of the cathode ray tube.

The position of the coil longitudinally along the neck of the tube is usually fixed in conventional designs and no operational adjustment is provided.

In addition to the above requirements, it is desirable that lateral adjustment does not affect the tilting adjustment or vice versa. It is also desirable that the controls be arranged in such a manner that they are accessible and that they further provide micrometric movement of the coil.

I-Ieretofore, the initial focusing and centering of the image spot on the face of a cathode ray tube has been a difficult and tedious process because of the fact that the tilting or angular adjustment of the focusing coil changed the lateral adjustment and vice versa. This difficulty was due to the fact that no means had been devised to bring the electrical center of the field into alignment with the mechanical center of rotation.

It is an object of this invention to overcome this difiiculty.

It is another object of this invention to provide an adjustable focusing coil for magnetic typ. cathode ray tubes in which the lateral adjustment is electrically independent of the angular adjustment and vice versa.

Another object of this invention is to provide an adjustable focusing coil capable of micro- I metric movement of the coil during the adjustcoil to form an angle with the neck of a cathode ray tube.

These and other objects will become apparent from the following specification when taken with the accompanying drawings in which:

Fig. l is a cross-sectional view coil in its housing;

Fig. 2 is a top view in partial section of the focusing coil in its housing; and

Fig. 3 is an exploded view of the coil cartridge and its assembly in one embodiment of the inof the focusing vention. I

Referring to Fig. 1, the focusing coil to is contained in a cartridge comprising housing H,

core ring l2, gap ring l3, and cap [4. Housing ll, core ring l2, and cap 14 are of magnetic material but the gap ring I3 is of brass or other suitable non-magnetic material. The gap ring is the essence of the operation of a focusing coil since it breaks the continuity of the magnetic path. Because of the gap, some of the flux, generated by a current through the focusing coil, enters the space inside the cathode ray tube through which the electrons pass. It is this portion of the magnetic field, which causes the electrons to be deflected from their straight line motion. If the magnetic field inside the tube is maneuvered correctly, the electrons can be deflected in such manner as to focus at the face of the tube. Ring [5 is a spacer ring of electric insulation to provide clearance for the coil leads and terminals. It also prevents movement of the coil within the case.

In Fig. 2 is disclosed the manner in which the coil leads [6 are soldered at the base of terminals l1 and 18.

By referring to Fig. 3, the assembly of the coil cartridge in the gimbal rings can be explained. The coil cartridge l2 seats in the inner gimbal ring [9. The inside diameter of i9 is reduced in such manner to form a ridge and thus allow the coil cartridge to seat at the proper level, so that the pivot points of the gimbal rings coincide with the electrical center of the magnetic field. A retainer ring fits over coil cartridge I2 and fastens to inner gimbal ring l9. Four screws 20a, 20b, 29c, and 26d fit through holes 2 I, 22, 23, and 24 of retainer ring 26 and screw into threaded holes l9a, I91), I90, and 19d to secure the coil cartridge between retainer ring 20 and inner gimbal ring [9.

Inner gimbal ring l9 fits into outer gimbal ring 25 so that the L-shaped extension 26 lies opposite the inclined ramp 21 and extension 28 is opposite extension 29. Between 28 and 29 is placed a sprin 39 which is held in place by a boss on each extension.

Lock screw 3| threads through hole 32 on outer gimbal ring 25 and through hole 33 on inner gimbal ring 19. The tip of 3! presses against coil cartridge 12 at an axial position coinciding with the center of the gap ring 13. Lock screw 34 threads through holes 35 in outer gimbal ring 25 and 36 in inner gimbal ring I9. It presses against coil cartridge [2 at a point also in the center of the gap ring 13. The tips of these two lock screws are directly opposite each other and thus provide the pivot points for inner gimbal ring 19 to pivot with respect to outer gimbal ring 25.

There is an adjusting screw 31 which threads through hole 38 on the L extension 26 and its point operates against the inclined ramp 21 on outer gimbal ring 25. The point is tapered to fit the slope of the ramp and is so located that when the planes of the two rings coincide the point of the screw is midway on the ramp.

The assembly consisting of outer gimbal ring 25, inner gimbal ring 19, coil cartridge 12 and re-- tainer ring 20, now fits into plate 39 in such orientation that L extension 40 is opposite inclined ramp 4| and extension 42 with a boss on it, is opposite boss 43 on plate 39. Spring 44 goes between extension 42 and boss 43. Lock screw 45 threads through hole 45 in ear 41 on plate 39, through hole 48 in outer gimbal ring 25 and its tip terminates in an axial position slightly removed from inner gimbal ring l9. Lock screw 49 threads through hole 50 in ear 5! of plate 39, through hole 52 in outer gimbal ring 25 and its tip occupies an axial position slightly removed from inner gimbal ring [9 at a point opposite the tip of lock screw 45. The two points allow outer gimbal ring 25 to pivot with respect to plate 39. There is an adjusting screw 53 which threads through hole 54in L extension 40. Its tip is tapered to follow the slope of inclined ramp 4! on plate 39 and is so located that when the planes of ring 25 and plate 39 coincide, the tip is midway on the ramp. Plate 39 fits on plate 55 in such manner that it is free to move laterally with respect to plate 55, between shoulders 56 and 51. Adjusting screw 58 which controls this lateral movement threads through hole 59 in L extension 66 on plate 55 and has a shoulder which is a running fit in ear SI of plate 39. Bolt '63 slides through adjusting screw 58 and is held in place by lock nut 64. When bolt 63 is in place, its head fits against the inside face of ear 6|.

Plate 55 sits on plate 65 in such manner as to align hole 66 in shoulder 51 with hole 61 in car 68[ Plate 56 is free to move laterally with respect to plate 65 in slides 69 and 10. This lateral movement is controlled by adjusting screw 1|, which threads through hole 61. It has a shoulder which is a running fit in hole 66 and is held in place by bolt 12 and lock nut 13 in an arrangement identical to that of adjusting screw 58.

Post 14 seats in hole 15 of clamp dog 16 and the extension of post 14 which is of a reduced diameter fits into hole 11 of plate 65. A tapered pin 13 fits into hole 19 and secures post 14 to plate 65. Clamp screw threads through hole 8| and it tip is tapered to operate against the inclined ramp 82. By tightening clamp screw 80. its tip presses the clamp dog 82 down against plate 39. thereby clamping both plates 39 and 55 against base plate 65 and securing the three plates against vibration or other factors tending to change their relationships. Another clamp dog assembly 83 is secured to base plate 65 through hole 84 in an identical manner to aid in holding the three plates together.

In operation, the neck of a magnetic cathode ray tube fits through hole 85 of the coil cartridge l2. When the tube is operating in its static state, the design of the control circuits should be such that the image spot appearing on the face of the tube is approximately focused and centered. If the spot is in this approximate state, it can be more accurately focused and centered by the adjustment of the control screws, embodied in this invention, in a manner to be discussed below.

The hermetically sealed focusing coil l2, designed as an easily replaceable unit, is carried on two gimbal rings, 19 and 25, which are adjustable by means of two screws, 31 and 53. The coil cartridge is rigidly secured to the inner gimbal ring by retainer ring 23, so that it must move with the inner gimbal ring in any direction which the ring may take.

The inner gimbal ring I9 pivots with respect to outer gimbal ring 25 on an axis determined by the screws 3| and 34. The focusing coil is so I 0- sitioned that the electrical center of the magnetic gap coincides with the inner gimbal ring pivotal axis. The extension spring 30 tends to keep the inner gimbal ring l5 tilted with respect to the outer gimbal ring 25. The extent of this tilt is determined by the position of the tapered tip of adjusting screw 31. This tip of screw 31 is tapered to fit the slope of the inclined ramp 21 and is so located that when the plane of the two rings. coincide, the tip of the screw is midway on the ramp.

above.

' The outergimbal ring 25 is tr somewhat similar construction differing only in size and orientation from ring I9. This outer ring pivots with respect to sliding plate 39 on an axis determined by screws 55 and 49. The pivotal axis of gimbal ring 25 is at right angles to that of ring I 9 by design. Extension spring 44, tends to keep the outer gimbal rin 25 tilted with respect to the plane of the sliding plate 39. The extent of this tilt is determined by the position of the tapered tip of adjusting screw 53 which is tapered to fit the slope of the inclined ramp 4| and is so located that when the plane of the outer gimbal ring coincides with that of plate 39, the tip of screw 53 is midway on the ramp. Therefore, adjusting screw 53 determines the tilt of the assembled combination of outer gimbal ring 25, inner gimbal ring it, and focusing coil cartridge l2 with respect to plate 39. Since the two rings are pivoted at right angles to each other, a combination of adjustment of the two tilting screws, 31 and 53, will provide any angular adjustment with respect to plate 39 within limits determined by the length of the inclined ramps 21 and 4|.

The gimbal rings, then, provide for any small angular adjustment of the coil with respect to the neck of the cathode ray tube which may be needed to aid in focusing the electron stream.

Sliding plates 39 and 55 with their respective adjusting screws 58 and H provide for small amounts of lateral adjustment. Plate 39 rides on plate 55 and is guided in its lateral movement by shoulders 56 and 51. The ear 6| of plate 39 is held between the head of bolt 63 and the shoulder of adjustment screw 58. The tip of screw 58 is a sliding fit in hole 62 of ear 61 but the diameter of the segment of screw 58 containing the threads is larger. This enlarged part of screw 58 provides the shoulder mentioned Hence when adjustment screw 58 is screwed inward or outward through threaded hole 59, a lateral movement is imparted to plate 39 and the gimbal ring assembly.

Plate 55 rides on base plate 65 and is guided in its lateral movement by slides 69 and 10. The shoulder 51 of sliding plate 55 is held between the head of bolt 12 and the shoulder of adjusting screw 1| so that when this adjusting screw is rotated clockwise or counterclockwise, plate 55 receives a lateral movement. Plates 39 and 55 move laterally at right angles to each other so that a combination of adjustments of screws 58 and II will center the image spot on the face of the tube. These lateral adjustments do not disturb the angular adjustment previously set in.

The four adjusting screws 31, 53, 58 and H are positioned radially with respect to the coil for operational convenience and further to permit a deflection coil to be placed adjacent to the focusing coil if required.

The invention described in the foregoing specification need not be limited to the details shown, which are considered to be illustrative of one form the invention may take.

What is claimed is:

1. In combination, a focusing coil for a cathode ray tube or similar device, a pair of gimbal rings, means securing said coil within one of said gimbal rings, a pair of sliding plates, means permitting said pair of gimbal rings to tilt with respect to said pair of sliding plates, means for controlling the amount of said tilt, a fixed plate, means for permitting'said sliding plate to move laterally with respect to said fixed plate, and means for controlling the amount of said lateral movement.

' 2'. An adjustable focusing coil comprising, an

electromagnetic core, a coil of wire wound thereon, a housing of electromagnetic material for said coil, a gap ring of non-magnetic material to mechanically and electromagnetically separate said core from said housing, a spacer ring to secure said coil in said housing, said coil, core, gap ring, spacer ring and housing being toroidally shaped, terminal posts mounted on said housing, means for connecting said coil to said terminal posts, means for hermetically sealing said coil in said housing, means permitting said coil to tilt in any direction, means for permitting the axis of said tilt to coincide with the mechanical center of said gap ring, a fixed base plate, means for permitting the movement as a unit of said coil and said tilt means in any direction laterally with respect to said fixed base plate without changing the tilt of said coil, and means for permitting micrometric movement of said coil in said directions of tilt and lateral movement.

3. An adjustable focusing coil comprising, an electromagnetic core, a coil of wire wound thereon, a housing of electromagnetic material for said coil, a ap ring of non-magnetic material to mechanically and electromagnetically separate said core from said housing, said coil, core, gap ring, spacer ring and housing being toroidally shaped, terminal posts mounted on said housing, means for connecting said coil to said terminal posts, means for hermetically sealing said coil in said housing, a gimbal ring including means for securing said gimbal ring around said housing, a second gimbal ring including means permitting said first gimbal ring to tilt with respect to said second gimbal ring, a sliding plate including means permitting said second gimbal ring to tilt with respect to said sliding plate, a second sliding plate including means permitting movement of said first sliding plate laterally with respect to said second sliding plate, a base plate including means for permitting movement of said second sliding plate laterally with respect to said base plate, and means for securing said first and second sliding plates to said base plate.

4. An adjustable focusing coil comprising, an electromagnetic core, a coil of wire wound thereon, a housing of electromagnetic material for said coil, a gap ring of non-magnetic material to mechanically and electromagnetically separate said core from said housing, a spacer ring to secure said coil in said housing, said core, coil, gap ring, spacer ring and housing being toroidally shaped, terminal posts mounted on said housing, means for connecting said coil to said terminal posts, means for hermetically sealing said coil in said housing, a gimbal ring into which said coil seats, a retainer ring which fits over said coil housing and bolts to said gimbal ring for securing said coil to said gimbal ring, a second gimbal ring into which said first gimbal ring fits including two lock nut type screws diametrically opposite each other for permitting said first gimbal ring to tilt with respect to said second gimbal ring, an extension spring arrangement tending to tilt said first gimbal ring with respect to said second gimbal ring, an adjusting screw and inclined plane arrangement for controlling the degree of said tilt, a sliding plate into which said second gimbal ring fits including two lock nut type screws diametrically opposite each other and at right angles to said first pair of screws for permitting said second gimbal ring to tilt with respect to said sliding plate, a second extension spring arrangement tending to tilt said second gimbal ring with respect to said sliding 7 plate, a second adjusting screw and inclined pla arrangement for controlling the degree of sai last-mentioned tilt, a second slidin plate a ains which said first sliding plate fits and with respect to which said first sliding plate is permitted to move laterally including two shoulders for guiding said lateral movement, a third a just n screw arrangement for controlling the amount of said lateral movement, a base plate into which said second sliding plate fits and with. respect t which said second slidin plate is permitted to move laterally including slides for gui ing sa lateral movement, said slides at right scal s to said shoulders of said second slidin plate, a

fourth adjusting screw arrangement for controlling the amount of said lateral movement of said second sliding plate with respect to said bas plate and two clamp dog-screw arrangements for securing said first and second sl din plates to said base plate.

5. An adjustable focusing coil for an electr ni device comprising, an electromagnetic core, a coil of wire wound thereon, a housing for said coil, a ring of non-magnetic material for separating said core from said housing, means for tilting said coil in any direction relative to the axis of said device, means independent from said tilting means for moving as a unit said coil and said tiltin means in any direction laterally relative to said device without changing the tilt of said coil, and micrometric means for fine adjustment of any of the movements of said coil.

6. An adjustable focusing coil for an electronic device comprising, an electromagnetic .core, a .coil of wire wound on said core, a housing for said coil, a ring of non-magnetic material separating said core from said housing, said ring being disposed about said core and positioned forbrea'king the continuity of the magnetic path associated with said coil, means for tilting said coil in any direction relative to said device and means independent from said tilting means for moving as a unit said coil and said tilting means in any direction laterally relative to said device, said any tilt direction remaining the same independently of the operation of said lateral moving means.

"7. An adjustable focusing coil com-prising, an electromagnetic core, a coil of wire wound on said core, an electromagnetic housing for said coil, a ring of non-magnetic material separating said core from said housing, a fixed baseplate, means for tilting said coil in any direction relative to said base plate, means operable independently of said tilting means for-moving as a unit said coil and said tilting means in any direction laterally with respect 'to said base plate without changing the tilt of said coil, and micrometer screw devices for adjusting the position of said coil in any desired direction.

8. In combination, a focusing coil for an electromagnetic device, a housing for said coil, 3, sim ring inclu g me ns for securing aid ,gimbal ring around said housing, a second gimbal ring mcludine means permitting said first imbal ring to til wi h r spec to sai secon gimbal ring, a first sliding plate includ ng mean permitting said s co d s mbal ring to tilt wit res ect t. .said s idinepl te, .a second pla including means permitting incitement ,of said first sliding plate laterally with respect to sa second plate, a base plat i cludin ime ns o permitting movement of said Second-finding Plate laterally with respect to said base pla e, an .means for securing said first and second slidin plates to saidhase plate.

9.. In. combina io a focusing oil fo an e c rom g e c d i e, m n fo il ng sa d co l in any dir c n ela i e to the x of sai devic and m a s ind pen n rom d i t ng ea for moving said coil and said tilting means as a unit in any direction laterally relative to said device without changing the tilt of said coil,

10, In combination, a focusing coil for an 81%- troma n tio device, a ase P e fixe ith respect to said device, means for tilting said coil in any direction relative to said base plate, means operable independently of said tilting means for moving aid coil and said til g means as a un any irection laterally with respect to said ase plate and said device without altering the tilt of said coil s determined by said tilting m a s.-

11. c mbination, a fo using coil f r a oathode ray tube or similar devic fi d s ond cooperating gimbal ri gs, means s cu ing s i coil within aid firs gimbal rin first nd secon s id n p ates, mea s supp ting a d ec nd gimbal ring on said first sliding plate and arranged to permit said first and second gimbal rings to tilt with respect to said sliding plates, a third plate fixed in position with respect to said cathode ray tube, means secured to said third plate and arranged to permit lateral movement of said second plate thereon in one direction, m ans secured to sa d s cond plate and arran t p m a al mo em nt o said first Pist thereon in a direction transve se t s d d m ion- 1 n ad st le f us n c il 9! a cath d ray tube, or the like, oomp is n in oo nns i with said coil, a base plate fixed po tion relative to said tube, a firs plate slidably mou ted o said base plate for movement in one dire tion relative to said base plate, a second plate slidanly mounted on said first plate for movement relative thereto in a direction transverse to said one direction, a first gimbal ring pivota'lly mounted on said second :plate, .a second gimbal ring pivotally mounted within said first gimbal ring, and :means securing said .coil within said second gimbal ring.

13. .An adjustable focusing coil for a cathode ray tube, or the like, comprising, in combination with said coil, a base :plate fixed in position with respect to said tube, afirst .plate slidably mounted jonsaid base plate for movement intone direction, a secondplate slidably mounted on said'fi-rst plate for movement relative thereto in a direction transverse to said .one direction, and means surrounding said coil and pivotal'ly mounted on said second plate for tilting said coil in any direction relative to the axis of said tube.

CEGIL WALTON.

References Cited in the file of this patent UNITED STATES PATENTS 

